Biomass feedstock, such as agriculture and forestry residues, plays an important role in developing alternatives to fossil fuels. Although there are several methods of generating energy from biomass, gasification, in which a hydrogen-carbon monoxide gas mixture (syngas) is produced, offers several advantages. For example, syngas, like natural gas, can be burned in gas turbines, which are more efficient than steam boilers. Another key feature of syngas is, like petroleum products, it can be converted to useful chemicals, including dimethyl ether (DME). Syngas is also an available “raw” fuel from sources other than biomass, such as from coal gasification and natural gas stem reforming and other sources.
DME can be used as building blocks for synthesizing important chemicals, including dimethyl sulfate, high value oxygenated compounds, and lower olefins. Because of its environmentally benign properties, it can also be used as an aerosol propellant in products such as hair spray and shaving cream. Recently, DME has been suggested as an alternative fuel for diesel engines. Engine performance tests indicate that DME has thermal efficiencies equivalent to traditional diesel fuel. Other advantages of using DME as a diesel replacement include the reduced NOx emissions, near-zero smoke production, and less engine noise. However, there are obstacles to producing DME from biomass syngas at an economical scale. For example, unlike petroleum, coal, and natural gas plants, which are established for central, large-scale applications, biomass feedstock and gasification systems are widely distributed geographically. If conventional DME process technology is adopted, a scale of 2500 t/d may be required for production economically comparable to conventional LPG fuel. Because it is difficult to deliver enough biomass to satisfy this criterion using conventional technology, a more compact and efficient portable process for converting the biomass or other source of syngas to DME is needed.